When designing loudspeaker boxes the predominant design principle consists in the box being built as a rectangular parallelepiped with five plane walls and a front panel for mounting the loudspeaker element. This method of construction enables the use of standard materials such as plywood panels, chipboards etc. With this design every plane surface has a natural frequency and the vibration of the surface is mechanically linked to the vibrations of the other surfaces via the joints at the edges of the box, thus resulting in a complicated pattern of natural vibrations which are felt as noise vibrations if the natural vibrations become excessive. In order to reduce this problem it is possible to fit within the loudspeaker box a lattice system directly linking the surface vibrations to one another, and the natural vibration problem can be reduced by joining in this way surfaces with different natural frequencies. It is, however, difficult, by such means to prevent natural vibrations entirely without a loudspeaker box constructed in accordance with the above principle having the characteristic that certain sound frequencies are amplified more than others thus resulting in not entirely natural sound reproduction.
The invention is based on the idea that another method of avoiding undesirable natural vibrations consists in designing the peripheral surfaces of the box as far as possible as twin-curved surfaces with each surface having a continuously varied radius of curvature. A surface designed in this manner does not possess a natural frequency in its proper sense, at any rate within the range audible to a human being. A further improvement is achieved, if the inner and outer peripheral surfaces of the loudspeaker box are not at a constant distance from one another and are mechanically linked.